The production of semiconductor components in many cases requires the production of a foreign material layer, that is to say a material layer which is not composed of a semiconductor material, in a semiconductor body. Such material layers are for example dielectric layers which are used as a capacitor dielectric in capacitors or which are used as a gate dielectric, field plate dielectric or as a drift control zone dielectric in MOS transistors. Furthermore, such material layers can also be composed of a conductive material such as, for example, a metal or a metal-semiconductor compound.
In a known method for the production of such a foreign material layer, a trench is produced, which extends into the semiconductor body, a material layer is applied to opposite sidewalls of the trench and the material layer is subsequently removed again from one of the two sidewalls, such that a material layer remains only at one of the two sidewalls. The removal of the material layer from one of the two sidewalls is effected by using an etching process, for example. Before the etching process is carried out, in this case a protective layer is applied to that part of the material layer which is not intended to be removed.
The protective layer is for example a photoresist, which is initially applied to both sidewalls but which is subsequently exposed and developed only in the region of one sidewall and the developed and undeveloped regions of which are subsequently etched selectively with respect to one another, such that a protective layer formed by the photoresist remains on one of the two sidewalls. Whether the developed or undeveloped part of the photoresist layer is removed depends on the type of resist (positive or negative) and the etching material used.
Precisely in the production of material layers which are intended to extend deeply into the semiconductor body in a vertical direction of the semiconductor body and in which correspondingly deep trenches are to be produced, the exposure of a photoresist at only one of the sidewalls is difficult, however. In this case, problems can arise as a result of a nonuniform exposure which can result from reflections of the light used at the trench sidewalls.